Combining both a pressure sensor and a temperature sensor in a single package can reduce overall sensor cost in control or telemetry applications where it is necessary to measure more than one parameter of fluid media in a vessel. For example, various automotive suppliers produce and sell sensors designed to mount on the intake manifold of an internal combustion engine for measuring both the absolute pressure (MAP) and the temperature (MAT) of air in the manifold. Typically, the sensor package includes a measurement port that passes through a wall of the intake manifold into the manifold air stream, and a pressure sensor sealed against the inboard end of the port. The manifold air temperature is measured by a thermistor disposed in the manifold air stream but within the port, and the leads of the thermistor are terminated in the sensor package adjacent the pressure sensor. One example of such a sensor is the MAP/MAT Sensor manufactured and marketed by Delphi Corporation.
While the above-described sensor configuration can be used to advantage in low-pressure applications (i.e., 15 p.s.i. or less), it is problematic in high-pressure applications (such as a turbocharged engine) due to the difficulty of forming a leak-free seal around the leads of the thermistor, even if the sensor housing is molded around the leads. Leakage around the sensor leads is undesirable not only because of manifold air pressure loss, but also because the manifold air (or other media) can contaminate the pressure sensor and associated electronic devices. Accordingly, what is needed is a combined pressure/temperature sensor that is particularly suited to high-pressure applications.